Re: [PATCH 00/16] dts/dt-bindings: Fix Arm Ltd. ARMv8 "boards"

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On Tue, May 5, 2020 at 12:52 PM Robin Murphy <robin.murphy@xxxxxxx> wrote:
>
> On 2020-05-05 5:51 pm, Andre Przywara wrote:
> > Date: Mon, 4 May 2020 12:43:18 +0100
> > Subject: [PATCH 03/16] dt-bindings: ehci/ohci: Allow iommus property
> >
> > A OHCI/EHCI controller could be behind an IOMMU, in which case an iommus
> > property assigns the stream ID for this device.
>
> Hmm, pretty much any DMA master device could be behind an IOMMU, and in
> a way that's basically entirely irrelevant to the device itself (and
> thus the consumer of its binding). Is there a better way we can handle
> this than repeating such "semi-standard" properties in individual
> bindings for ever more?

We did that for pinctrl-* properties which I was somewhat lukewarm on.
I think a lot more nodes have pins than DMA, so I prefer to keep this
explicit. We do allow more than 1 iommus entry which might be device
specific, so somewhere we need to capture how many are allowed/valid.

We could define a 'dma-device.yaml' schema and reference that on all
DMA capable device. Not sure that saves much though.

Rob



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